Despite its prevalence, decades of research have failed to yield an FDA-approved medication for the treatment of cocaine addiction. The lack of viable pharmacotherapeutic approaches is attributable, in part, to fundamental gaps in our understanding of the situations and underlying neurobiological processes that promote relapse to drug use in abstinent cocaine addicts. It is well established that stress is an important contributor to drug relapse. Considering its pervasive and unavoidable nature, this relationship between stress and drug use is highly problematic. Recent findings indicate that the role of stress in relapse is more complex than once believed and that, rather than simply triggering cocaine use, stress can indirectly promote drug relapse by heightening sensitivity to drug-associated stimuli. Our team has established a self-administration/reinstatement rat model for examining this stage-setting role for stress in cocaine seeking. Using this model, we have demonstrated that the ability of a stressor (electric foot shock) to promote reinstatement by an otherwise subthreshold priming dose of cocaine requires increases in corticosterone and activation of CB1R cannabinoid receptors. Moreover, our preliminary findings have localized this mechanism to the prelimbic cortex (PLC), a source of glutamatergic projections to the nucleus accumbens core that have been shown to be critical for cocaine use. This collaborative multi-PI proposal brings together a multi-disciplinary team of scientists to test the hypothesis that, durin stress, corticosterone enhance endocannabinoid signaling in the PLC, thereby suppressing GABAergic neurotransmission and disinhibiting pyramidal neurons that project to the nucleus accumbens core. This stage- setting mechanism allows for subthreshold doses of cocaine to induce reinstatement. Aim 1 of the proposal will examine the role of stress-induced increases in endocannabinoids in the PLC, with a focus on 2-AG, and the resulting activation of CB1 receptors in the stress-induced potentiation of cocaine seeking. Aim 2 will investigate the role of corticosterone regulation of endocannabinoid signaling in the PLC in the effects of stress on cocaine seeking and the mechanisms through which this regulation occurs. Aim 3 of the proposal will examine how these stress-induced alterations in the PLC disrupt GABAergic regulation of pyramidal neurons that project to the nucleus accumbens core to promote cocaine use. The findings from these proposed experiments have the potential to lead to the development of new and more effective treatment approaches for the management of cocaine addiction. However, the importance of defining the mechanisms through which stress alters cortical regulation of this pathway extends beyond addiction and should guide our understanding of how stress regulates motivated behavior in general and therefore how it contributes to a range of neuropsychiatric conditions.